The invention relates to optical signaling and waveguides utilized in such signaling.
Optical circuits offer advantages over traditional electrical circuits, particularly in the perceived ability to provide higher speed data transmissions. Such transmissions may take place not only between computers, but also within machines, in which case board-to-board and chip-to-chip data communication using optical circuits can be utilized.
In a conversion area of a light signal and an electrical signal, a light transmission path including an optical fiber or an optical waveguide, or a photoelectron conversion element (e.g., laser diode, photodiode, etc.) may be used. A circuit for optical information processing, e.g., an optical electronic integrated circuit (OEIC), typically may include a combination of a light transmission path or photoelectron conversion element(s), and a circuit (e.g., an integrated circuit for controlling an electronic element, processing an electronic signal, and/or a circuit for driving an electronic part).
An optical waveguide may be used, in one example, to couple an optical signal with an OEIC. In an optical waveguide, control of an index of refraction is necessary for a single mode light transmission. The typical optical waveguide includes a core portion and a cladding portion disposed above the core portion. The index of refraction of the cladding portion is generally slightly lower than the index of refraction of the core portion. For example, a typical specification for a silicon dioxide (SiO2) based single mode waveguide core and cladding portion includes a core size on the order of 6 to 8 microns by 6 to 8 microns, with a difference between an index of refraction of the core portion and that of the cladding portion on the order of about 0.25 percent.
As noted above, an important property of a waveguide lies in the difference in the index of refraction of the core and the cladding. In general, the difference in the index of refraction between the core portion and the cladding portion determines the amount of reflection of a light transmission through the waveguide. In the single mode waveguide, one objective is for total internal reflection within the waveguide. Silicon dioxide based waveguides (i.e., where the core and cladding portions are both silicon dioxide) are limited in their index of refraction difference between the core portion and the cladding, such limit generally determined by the amount of dopants added to the cladding portion.
What is needed is an improved waveguide.